1. Field of the Invention
This invention is in the field of metal working; more specifically the invention is related to tools employed for straightening dents in sheet metal using a welded stud to pull the dent out.
2. Background Art
Sheet metal panels, such as those found in automobile bodies, are accidentally dented. If the backside of the dent is accessible, as on a fender, the dent can be straightened with a hammer. But if the backside of the dent is concealed, as on a door, more complicated methods are generally used.
For example, it is known in the art to straighten such a dent by attaching an elongated tool to the exposed side of the dent and then "pulling" the dent out by hammering on an anvil member anchored to the tool. The tool may be attached to the dent magnetically, and a slide hammer mounted integrally on the tool shaft as described in U.S. Pat. No. 2,605,658.
Alternatively, a metal stud may be welded to the exposed side of the dent and hammer means then attached to the stud to pull the dent out. The stud is then cut off and ground down before refinishing the panel. U.S. Pat. Nos. 2,847,557; 4,160,148; and U.S. Pat. No. 4,562,328 disclose welding guns especially suited for welding studs. U.S. Pat. No. 3,801,772 discloses a tool for repairing dents which incorporates a stud welding gun and hammer means in the same tool. However, when using any of the tools of the prior art to straighten a dent, it is necessary, after the dent is straightened, to cut the stud off and then grind or file it flush with the panel before refinishing. These operations are time consuming and inefficient.
It is, therefore, one objective of this invention to provide a tool for straightening a dent in a meal workpiece and a method of using it which avoids the cutting and grinding steps associated with the prior art welded stud technique. It is another objective of this invention to provide a welding gun which can be used for either stud welding or spot welding by simply exchanging the electrode. Other objectives will be evident to those skilled in the art of metal working, to whom this application is directed.
The aforesaid objectives are accomplished by providing a tool which includes, not only an elongated welding gun having a welding electrode removably attached thereto for welding a stud to a dented workpiece, but also hammer means as an integral part of the tool, and means for delivering sufficient electric power to remove the stud by dewelding it, thereby avoiding the cited inefficiencies of the prior art.